filter_geom {gdalcubes}

Filter data cube pixels by a polygon

Description

Create a proxy data cube, which filters pixels by a spatial (multi)polygon For all pixels whose center is within the polygon, the original

Usage

filter_geom(cube, geom, srs = NULL)

Arguments

cube

source data cube

geom

either a WKT string, or an sfc or sfg object (sf package)

srs

string identifier of the polygon's coordinate reference system understandable for GDAL

Details

The resulting data cube will not be cropped but pixels outside of the polygon will be set to NAN.

If geom is provided as an sfc object with length > 1, geometries will be combined with sf::st_combine() before.

The geometry is automatically transformed to the data cube's spatial reference system if needed.

Value

a proxy data cube object

Note

This function returns a proxy object, i.e., it will not start any computations besides deriving the shape of the result.

Examples

# create image collection from example Landsat data only 
# if not already done in other examples
if (!file.exists(file.path(tempdir(), "L8.db"))) {
  L8_files <- list.files(system.file("L8NY18", package = "gdalcubes"),
                         ".TIF", recursive = TRUE, full.names = TRUE)
  create_image_collection(L8_files, "L8_L1TP", file.path(tempdir(), "L8.db"), quiet = TRUE) 
}

L8.col = image_collection(file.path(tempdir(), "L8.db"))
v = cube_view(extent=list(left=388941.2, right=766552.4, 
              bottom=4345299, top=4744931, t0="2018-01", t1="2018-06"),
              srs="EPSG:32618", nx = 497, ny=526, dt="P1M")
L8.cube = raster_cube(L8.col, v) 
L8.cube = select_bands(L8.cube, c("B04", "B05")) 
L8.ndvi = apply_pixel(L8.cube, "(B05-B04)/(B05+B04)", "NDVI")
WKT = gsub(pattern='\\n',replacement="",x = 
  "Polygon ((-74.3541 40.9254, 
             -73.9813 41.2467, 
             -73.9997 41.4400, 
             -74.5362 41.1795, 
             -74.6286 40.9137, 
             -74.3541 40.9254))")
L8.ndvi.filtered = filter_geom(L8.ndvi, WKT, "EPSG:4326")
L8.ndvi.filtered

plot(L8.ndvi.filtered)